The impact of packaging materials on the product contained has for some time been recognized when dealing with brew-in packets of the type utilized with beverages such as coffee and tea. In particular, U.S. Pat. No. 1,247,906 issued to Tully on Nov. 27, 1917, discloses a tea-ball for marketing and brewing tea. The ball is made in two sections of paper or similar material. In order that the tea-ball may withstand hot or boiling water, each section is coated with a waterproofing, heat-resisting and cementitious substance, preferably a solution of cellulose acetate. The coating is chosen so that it will not affect the taste or quality of the beverage brewed when the ball is immersed in hot water.
Similarly, U.S. Pat. No. 3,183,096 issued to Hiscock on May 11, 1965, discloses a porous brew-in packet for ground coffee made from synthetic filter paper designed not to damage the natural aroma and flavor of coffee nor impart any false flavor or taste or odor to the brewed coffee. According to the teachings of Hiscock, prior art efforts to adapt tea bag materials to package coffee were generally not successful since they failed to recognize that such materials would contribute to and accelerate the deterioration of coffee packed therein through acting as oxygen carriers. By way of contrast, the paper employed by Hiscock is preferably a porous synthetic fiber paper comprised of single filament polymeric fibers selected from the group consisting of nylon, polyesters, and acrylics bonded together by a taste-free, non-toxic dispersed polymer having a melting point in excess of the boiling point of water and substantially lower than the melting point of the polymer fibers which it bonds. The paper of the packet has its edges heat sealed at a temperature above the melting point of the dispersed binding polymer and below the melting point of the polymer fibers.
U.S. Pat. No. 3,373,043 issued to Rubenstein on Mar. 12, 1968, discloses a porous paper brew-in package for fresh coffee which is sized with a harmless water soluble material such as vinyl acetate acrylate copolymer to make it air impervious. According to Rubenstein, the package is heat sealed about its edges and, prior to brewing, protects the coffee from the atmosphere. During brewing, the water soluble sizing is dissolved and permits normal brewing to occur. After brewing, the entire package may be disposed of.
Finally, U.S. Pat. No. 2,805,164 issued to Doppler discloses a package in which finely ground coffee beans can be sold. The package is so formed that it holds the coffee air-tight so that it will keep its original quality, even though ground, and when properly opened the container will itself serve as a filtering medium, so that for the preparation of a cup of coffee all one needs do is to pour boiling water into the container and let liquid coffee drip out at the bottom. The outside of the package is formed from a layer of metal foil such as aluminium or tin foil which is preferably made in one piece and is bent along the crease line to form a square having foil on each face. The edges of the foil other than the bent edge formed at the crease line are sealed together, and in one corner the foil layers are pressed tightly together so that this corner may be readily identified as the corner to be torn off. Between the layers of foil a layer of filter paper is provided to encapsulate the ground coffee. The layers of foil are tightly sealed around their edges as by an adhesive or heat sealing or the like to produce a package which will be airtight to retain the good qualities of the coffee. When opened, the package will be in the form of a filter with the foil acting as a watertight funnel and the inner paper layer acting as a filter medium.
As will be appreciated by those skilled in the art, ground coffee products of the type disclosed in the aforementioned references have substantial naturally occurring aroma. Most instant coffee products, on the other hand, do not have significant naturally occurring aroma due to the manner in which they are processed. The lack of aroma impact when opening gas and moisture impervious containers of instant coffee product is extremely pronounced when dealing with relatively small individual serving style packets which are typically comprised of gas and moisture impervious flexible packaging films. To offset this initial lack of aroma impact, the aroma of instant coffee products is typically enriched by the addition of an aromatized oil such as coffee aroma oil thereto prior to or concurrent with packaging.
Particularly preferred method and apparatus for enriching the aroma of edible oils such as coffee oil and for enriching the aroma of instant coffee products using said aroma enriched oils are generally disclosed in the following commonly assigned patents which are hereby incorporated herein by reference: U.S. Pat. No. 3,625,704 issued to Andre et al. on Dec. 7, 1971; U.S. Pat. No. 3,769,032 issued to Lubsen et al. on Oct. 30, 1973; and U.S. Pat. No. 3,783,163 issued to Patel on Jan. 1, 1974. A particularly preferred method of enriching the initial aroma impact of individualized serving packets of instant coffee is disclosed in greater detail in the commonly assigned, co-pending patent application of Sally W. Reade, George D. Brown, Russell E. Parker and James E. Vogel entitled Single-serving Packets of Aromatized Instant Beverage, Ser. No. 183,491, filed Sept. 2, 1980 and hereby incorporated herein by reference.
In the method disclosed in the aforementioned patent application of Reade et al., a single serving packet comprised of gas and moisture impervious flexible packaging film and preferably having a product-contacting surface comprised of heat sealable film is formed by folding a continuous web about its longitudinal centerline, heat sealing the edges intermediate adjacent packets in said web, and spraying the interior surfaces of the three-sided packets thus formed with coffee aroma oil prior to addition of the soluble instant coffee product thereto. The packets are thereafter sealed at their open edge, preferably under an inert gas atmosphere, and cut from the continuous web to form individual serving packets. An object of the aforementioned patent application of Reade et al. is to provide a single serving packet of aroma enriched instant coffee product which has an improved initial aroma impact when opened without, at the same time, producing the appearance of oil on the beverage formed utilizing the product contained in the package.
It will be appreciated that instant coffee products of the type disclosed in the aforementioned patent application of Reade et al. are not packaged in brew-in packets, since the instant coffee is removed from the packet and completely dissolved in hot water to form the coffee beverage. Since the foil laminate materials disclosed in the application of Reade et al. are known to have good gas and moisture barrier properties, it was highly unexpected that the desired coffee aroma impact was not always present when packages of the aforementioned type were opened, even when a substantial quantity of coffee aroma oil had been added thereto prior to sealing. In further investigating this phenomenon it was observed that the intensity of the coffee aroma, as measured organoleptically, decreased noticeably over a period of a few weeks. Furthermore, gas chromotagraph readings taken of the head space of such packets revealed a substantial loss of certain of the volatile aromatic constituents from the packets only a few hours after sealing. These investigations led to the discovery that the volatile aromatic constituents were either absorbed or adsorbed by the heat sealable polymer utilized as the product-contacting layer in the gas and moisture-impervious packaging films from which the individual packets were formed.
Further investigation has revealed that not all heat sealable polymers react identically in this regard. The reaction of some heat sealable polymers proved to be adverse, while the reaction of other heat sealable polymers proved to be imperceptible under test exposures of approximately two weeks duration. Nonetheless, due to variations in product and aroma oil quality, packaging materials and conditions of storage, it is difficult to reliably predict which polymers will prove to be substantially inert to the aromatic volatiles over extended periods of time.
Accordingly, it is an object of the present invention to provide a flexible packet containing instant coffee product and coffee aroma oil which will present a high coffee aroma impact to the consumer upon opening, even after an extended shelf life in said flexible packet, without at the same time producing the appearance of oil on the beverage formed utilizing the product contained in the package.